1. Field
The present embodiment relates to an electrically powered vehicle provided with a traction motor.
2. Description of the Related Art
Japanese Unexamined Patent Application Publication No. 10-271605 describes technology for switching from regenerative braking force to frictional braking force in an electric vehicle when a battery that stores electricity, such as regenerated electrical power, has reached full charge.
For example, in a vehicle such as an electric vehicle, switching is made from regenerative braking force to frictional braking force when a battery for storing electricity, such as regenerated electrical power, reaches full charge, such as in the technology described in Japanese Unexamined Patent Application Publication No. 10-271605.
In particular, in order to realize braking like that of engine braking in an ordinary gasoline car or diesel car, braking force equivalent to engine braking and arising from regenerative braking force can also be realized in an electric vehicle. In such cases, when the amount of charging of the battery approaches a reference value acting as the limit for charging, conceivably a unit for implementing braking force equivalent to engine braking might make a smooth transition from regenerative braking force to frictional braking force by gradually reducing the regenerative braking force, and gradually increasing the frictional braking force. Generating frictional braking force is also conceivable in cases in which, relative to the braking force demanded by a driver, there is insufficient battery charge, or insufficient braking force due to regenerative braking force being limited in order to protect the battery.
The technology of Japanese Unexamined Patent Application Publication No. 10-271605 is technology to switch from regenerative braking to frictional braking in cases in which regeneration is limited due to a battery reaching full charge, or the like. Hitherto, when regeneration is limited, deficiencies in drive force demanded by a driver (drive force demand) have been supplemented by frictional braking force; however, fractional braking force cannot foe generated in cases in which there has been a breakdown in frictional braking force, or cases in which a rise in the temperature of brake components (brake pads or rotors) has occurred.
However, there is no mention in Japanese Unexamined Patent Application Publication No. 10-271605 regarding how braking force will be generated in cases in which frictional braking force cannot be generated under regeneration limiting.